Carbohydrate Structure and Function - I

Question 1

What is the empirical formula of carbohydrates?

Answer 1

(CH₂O)ₙ or Cₙ(H₂O)ₙ.

Question 2

What functional groups do carbohydrates contain?

Answer 2

Aldehyde (-CHO) or keto (C=O) groups.

Question 3

What is an asymmetric/chiral carbon?

Answer 3

A carbon with four different groups attached.

Question 4

What are enantiomers?

Answer 4

Mirror-image isomers (e.g., D-glucose and L-glucose).

Question 5

How are D and L forms determined?

Answer 5

By the configuration of the penultimate carbon (reference: glyceraldehyde).

Question 6

What are anomers?

Answer 6

Isomers differing at the anomeric carbon (C-1 for aldoses; α = OH down in Haworth, β = OH up).

Question 7

Name hexoses of biomedical importance.

Answer 7

Glucose, fructose, galactose.

Question 8

What is the clinical use of 50% glucose solution?

Answer 8

Treat hypoglycemia (rapid blood sugar restoration).

Question 9

What are deoxy sugars?

Answer 9

Sugars with a hydroxyl group replaced by hydrogen (e.g., deoxyribose in DNA).

Question 10

Compare glycosidic bonds in maltose, lactose, and sucrose.

Answer 10

Maltose: α-1,4 (glucose + glucose).

Lactose: β-1,4 (glucose + galactose).

Sucrose: α-1,2 (glucose + fructose).

Question 11

Why is lactose intolerance common?

Answer 11

Deficiency of lactase enzyme, leading to undigested lactose in the gut (symptoms: bloating, diarrhea).

Question 12

What is invert sugar?

Answer 12

Glucose + fructose mix (e.g., honey; formed by sucrose hydrolysis via invertase).

Question 13

Compare starch, glycogen, and cellulose.

Answer 13

Starch: Plant energy storage (amylose α-1,4; amylopectin α-1,4/α-1,6).

Glycogen: Animal storage (branched α-1,4/α-1,6).

Cellulose: Structural (β-1,4; indigestible by humans).

Question 14

What is dextran’s medical use?

Answer 14

Plasma volume expander and antithrombotic.

Question 15

What is chitin’s structure?

Answer 15

N-acetylglucosamine with β-1,4 linkages (found in arthropod exoskeletons).

Question 16

Name two glycosaminoglycans (GAGs) and their roles.

Answer 16

Hyaluronic acid: Lubricant in joints/vitreous humor.

Heparin: Anticoagulant in blood.

Question 17

What is peptidoglycan?

Answer 17

Bacterial cell wall component (NAM + NAG); targeted by penicillin.

Question 18

What does Benedict’s test detect?

Answer 18

Reducing sugars (free aldehyde/keto groups; e.g., glucose, not sucrose unless hydrolyzed).

Question 19

Name a derivative of carbohydrates used in medicine.

Answer 19

Ascorbic acid (vitamin C) or heparin (anticoagulant).

Question 20

Define mutarotation.

Answer 20

Spontaneous interconversion between α and β anomers in solution (e.g., glucose).

Question 21

What is the difference between furanose and pyranose?

Answer 21

Furanose = 5-member ring; pyranose = 6-member ring.

Question 22

How is sorbitol produced, and why is it clinically relevant?

Answer 22

Reduction of glucose; accumulates in diabetes (causing cataracts/peripheral neuropathy).

Question 22

What are amino sugars? Give an example.

Answer 22

Sugars with a hydroxyl group replaced by an amino group (e.g., glucosamine in cartilage).

Question 23

What enzyme deficiency causes sucrose intolerance?

Answer 23

Sucrase-isomaltase deficiency (CSID/GSID).

Question 24

What is inulin used for diagnostically?

Answer 24

Testing kidney function (filtered but not metabolized).

Question 25

Why can’t humans digest cellulose?

Answer 25

Lack of cellobiase (breaks β-1,4 linkages).

Question 26

What is the role of hyaluronidase?

Answer 26

Degrades hyaluronic acid (used in fertility treatments to help sperm reach the egg).

Question 27

How does trehalose differ from maltose structurally?

Answer 27

Trehalose: α-1,1 linkage (heat-resistant); maltose: α-1,4 linkage.

Question 28

Why is agar used in bacterial cultures?

Answer 28

Indigestible by bacteria; forms stable gels.

Question 28

What bonds create branching in glycogen?

Answer 28

α-1,6 glycosidic linkages (every 8–12 glucose units).

Question 29

How is iron sucrose used medically?

Answer 29

Treats iron deficiency anemia (IV formulation).

Question 30

What is dextrin’s role in food production?

Answer 30

Thickening agent in sauces/soups; filler in tablets.

Question 31

Why is honey antimicrobial?

Answer 31

High invert sugar concentration (low water activity inhibits microbes).

Question 32

What is the glycocalyx?

Answer 32

Carbohydrate coat on cell membranes (cell recognition/adhesion).

Question 33

How does penicillin target bacteria?

Answer 33

Inhibits peptidoglycan synthesis (disrupts cell wall).

Question 34

What are NAM and NAG?

Answer 34

Repeating units in bacterial peptidoglycan (N-acetylmuramic acid + N-acetylglucosamine).

Question 35

What is chondroitin sulfate’s function?

Answer 35

Structural component of cartilage/tendons (joint supplements).

Question 36

Why is heparin an anticoagulant?

Answer 36

Binds antithrombin III to inhibit clotting factors.

Question 37

What is agarose derived from?

Answer 37

Agar (used in DNA electrophoresis).

Question 38

Why can’t L-glucose be metabolized?

Answer 38

Hexokinase cannot phosphorylate it (D-form is enzymatically compatible).

Question 39

Which GAG is found in the vitreous humor?

Answer 39

Hyaluronic acid.

Question 39

What is lactase nonpersistence?

Answer 39

Genetic reduction of lactase after infancy (common in adults).

Question 39

How does glycogen’s structure suit its role?

Answer 39

Highly branched → rapid glucose release during fasting.

Question 40

Name a non-reducing disaccharide.

Answer 40

Sucrose (no free anomeric carbon).

Question 41

What sugar alcohol is linked to diabetic complications?

Answer 41

Sorbitol.